The present invention relates to the field of art dealing with projectiles. More particularly, the present invention relates to an apparatus which can be secured in a new or worn gun tube to obtain improved ballistic results.
A worn gun tube produces many variations in interior and exterior ballistic performance and makes the determinations of performance parameters unreliable. Gun tubes erode from repeated firings by the movement of high temperature gases and residues generated from burning propellant, by chemical action and by friction between the projectile and bore. As the gun tube erodes, the initial pressure required to accelerate the projectile is reduced and hot gases escape around the projectile causing increased wear and a substantial reduction in projectile velocity and launch stability. In order to solve this problem, the following two methods are known in the prior art.
First method is to machine or mold a rotating band or obturator of larger diameter than the eroded cross section of the barrel at the critical seat position. This requires a slightly larger band or obturator for each firing or several made to the same oversize diameter. However, the first band would be difficult to position properly and the last would tend to be easy to position properly.
A second method is to rechamber the gun tube in a machine shop, thereby making the gun tube shorter or boring out the chamber to replace the removed material with a sleeve having the original chamber dimensions.
The basic shortcoming in prior art methods have related to an absence of improved ballistic results. Further, said methods are time consuming and produce additional problems to the ballistician and test personnel. This problem has, in the prior art, proven to be a formidable one. Accordingly, the present invention is intended as a solution to said problems.